We have described the mechanism whereby zein, the major storage protein in corn, is synthesized and processed on membranes surrounding the protein bodies inside of which it is stored. The polysomal localization of zein messenger RNA to these specific organelles has provided a means for the purification of zein mRNA to apparent homogeneity. The fact that only zein is translated on these membranes indicates a useful system in which membrane bound translation and processing may be studied. Double strand cDNA from zein mRNAs have been cloned in a bacterial plasmid and restriction endonuclease fragments of these sequences together with zein mRNA will be used to obtain the nucleotide sequences of some of the major zein mRNAs. These cloned sequences will also be used to identify zein structural genes in maize chromosomal DNA and estimate their frequency. After in vivo translation zein polypeptides have a sequence of 10-20 amino acids removed from their amino terminus and are glucosylated. We will use membranes obtained from protein bodies to show that these events can be duplicated in a messenger dependent cell-free protein synthesizing system.